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Theoretical Atto-nano Physics
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2019
TWO emerging areas of research, attosecond and nanoscale physics, have recently started to merge. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femtosecond and sub-femtosecond timescales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds (1 attosecond = 1 as = 10 –18 s), which is of the order of the optical field cycle. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is ~152 as. On the other hand, the second topic involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the combination with intense laser physics is relatively recent.
Reflected and transmitted second harmonics generation by an obliquely p-polarized laser pulse incident on a vacuum-plasma interface
Published in Waves in Random and Complex Media, 2018
The achievement of generation of strong laser pulse by chirped-pulse amplification technology opened the new research of area called the laser-plasma interaction [1,2]. This interaction is used in the number of areas including laser-plasma acceleration [3–5], inertial confinement fusion [6,7], relativistic self-focusing [8,9], optical harmonic generation [10–18], photoelectron spectroscopy [19] and so on. High harmonic generation as a source of coherent light at short wavelength attracts great attention due to a wide range of applications, such as Extreme Ultraviolet (EUV) non-linear optics and attosecond physics. The high-order harmonic generation has been analyzed both experimentally and theoretically in the research related to laser-plasma interaction [11,17,20,24]. Among these, the second-harmonic (SH) generation has unique place in laser produced plasma [25,26]. The phase matching between the generated harmonic and fundamental waves has an important role in harmonic generation process. The phase-match relativistic third harmonic generation in forward direction have been experimentally observed by varying the temporal delay and the energy of the laser pulse [27]. In a plasma having density ripple, the ripple provides additional momentum required for resonant enhancement of harmonic power [28–32]. On the other hand, a transverse magnetic field can be introduced to provide the required additional momentum for the harmonic radiation [33–38]. In a plasma with a ripple density and in the presence of magnetic field, generation of SH becomes faster as magnetic field increases owing to the strong coupling between magnetic field and laser pulse, while ripple density provides phase matching between fundamental and SH beam [39]. It has been observed that self-focusing of laser pulse significantly affects the SH generation (SHG) in plasma [40–49].